1. Field of the Invention
The present invention relates to an antenna selection method and related device, and more particularly, to an antenna selection method capable of estimating wireless signal strength via weighted distribution and related device.
2. Description of the Prior Art
Advances in wireless network technologies, in addition to convenience and mobility of wireless networks, have led to an increasing amount of wireless communication network applications. Generally, in a wireless communication network, environmental effects cause wireless signals to suffer unknown phase shift and amplitude attenuation during transmission, resulting in interference in signals received by a receiving terminal and signal distortion, affecting signal transmission efficiency.
Therefore, to enhance signal transmission efficiency, conventional techniques often utilize antenna diversity techniques to solve the above-mentioned issues. Generally, antenna diversity mainly evaluates a wireless link according to measured signal strength information gathered at the receiving terminal, to determine a quality of received antenna signals, and selects a receiving antenna from multiple antennas to implement signal reception. For example, antenna diversity techniques often select an antenna with the strongest received signal strength from multiple antennas as the receiving antenna, to provide a user station to connect and start transmission. Please refer to FIGS. 1A and 1B, which are schematic diagrams of each antenna of a conventional wireless network system 10 during transmission with user stations, respectively. The wireless network system 10 includes an access point AP, antennas ANT1, ANT2 and user stations STA_A, STA_B. As shown in FIG. 1A, assume a received signal strength indication (RSSI) value of a packet signal of the antenna ANT1 received by the user station STA_A is −75 dBm, and a RSSI value of a packet signal of the antenna ANT1 received by the user station STA_B is −91 dBm. Therefore, for the antenna ANT1, an average RSSI corresponding to each user station is −83 dBm. Next, as shown in FIG. 1B, assume a RSSI value of a packet signal of the antenna ANT2 received by the user station STA_A is −82 dBm, and a RSSI value of a packet signal of the antenna ANT2 received by the user station STA_B is −86 dBm. Therefore, for the antenna ANT2, an average RSSI corresponding to each user station is −84 dBm. As such, the antenna ANT1 has a higher average RSSI value for each of the user stations; therefore, conventional techniques select the antenna ANT1 as the receiving antenna, such that the user stations STA_A and STA_B may connect to the access point AP via the antenna ANT1 to commence communication.
However, although the aforementioned antenna selection method ensures transmission and also a better connection quality between the user station having a higher RSSI value and a corresponding receiving antenna, the access point AP fails to cover as much range in the wireless network system as possible. For example, usually a RSSI of −80 dBm and above is considered excellent signal transmission strength; therefore, there is an optimal signal transmission between the antenna ANT1 and the user station STA_A in FIG. 1A. The RSSI value between the antenna ANT1 and the user station STA_B is −91 dBm, and the signal strength is considered too weak for connecting a transmission in practical operations. Conversely, as shown in FIG. 1B, RSSI values between the antenna ANT2 and the user station STA_A, and between the antenna ANT2 and the user station STA_B are −82 dBm and −86 dBm, respectively. Though not considered excellent, these signal transmission strengths still meet connection requirements for conducting normal communication and transmission. However, ultimately the antenna ANT2 is not selected for communication. In other words, for antenna selection, the prior art focuses on user stations with exceptionally strong signal strengths when signal strengths are stronger between the antenna and user stations, but neglects user stations having signal strengths that are not excellent, but nevertheless adequate for normal transmission. Simply put, though the above-mentioned conventional receiving antenna selection method ensures optimal connection quality between certain user stations and the receiving antenna, it precludes a transmission connection opportunity for other user stations, and thus reducing an overall signal transmission efficiency.
Furthermore, to obtain RSSI values of each receiving signals, the prior art directly obtains a RSSI for corresponding antennas recorded in baseband receiving signals, e.g. reading a RSSI value recorded in an address R50 of the receiving signals as signal strength information of the receiving signals. However, in such cases, the receiving signals may be a multicast beacon signal of the wireless network system or a unicast signal related to the corresponding access point. Since the prior art techniques are unable to determine whether or not a received signal is related to the corresponding access point when obtaining RSSI for receiving signals, the aforementioned unrelated signal strength information would easily be mistaken as basis for determination; as such, it is easy to mistakenly select an antenna with higher signal interference in an open network environment. In short, unless placed in a “clean” wireless network environment, antenna switching selection would be easily interfered by other surrounding wireless devices unrelated to the corresponding access point.